Explosives



Mardi 24, 1959 F. w. BROWN v ExPLosIvEs .Filed July 15, 1955 u mL INVENTOR Frederick Winfield Brown ,United States Patent This invention relates to explosives and particularly to a low cost explosive mixture having great shattering power and gas forming ability.

There has long been a need for a high performance, low cost, safe explosive for use in mining and related `industries and for other purposes where explosive mixtures may be used. Explosives of the xed type have long been known, such as mixtures of explosive hydrocarbons, including trinitrotoluene, nitroglycerine and nitrates absorbed on a solidmaterial or gelatinized in the form of cartridges. These iixed explosives have a relatively high eiciency but are comparatively expensive and are sensitive to shock. In an elort to overcome the expense of fixed explosives, it has heretofore been proposed to saturate carbon black with liquid oxygen for use as a low cost explosive. 'Ihese liquid oxygen-carbon black explosives are generally known by the term L.O.X.

jThe L.O.X. explosives are quite sensitive to lire and to impact detonation so long as sulcient oxygen for comybustion remains in the mixture.

They have the further disadvantage that a large excess of liquid oxygen must generally be addedin order to retain suicient oxygen in the mixture at the time when the explosion is desired. These two factors have made these L.O.X. explosives comparatively expensive and unsatisfactory for many uses. It has been propored to overcome the problems .of the L.O.X. explosives and the high cost of conventional ixed explosives by using a mixture of carbon black and ammonium nitrate to form a lixed explosive. In this vmixture the amount of combustible must be controlled within relatively narrow limits-or the explosive will be insensitive and cannot be detonated, and, even with the optimum mixture of vcarbon and ammonium nitrate, a relatively large amount of an expensive xed explosive `such as gelatin dynamite must be used with the am- 'monium nitrate and carbon to act a a booster in order to bring about the explosion. These ammonium nitrate carbon explosives do not have as high performance characteristics as the liquid oxygen carbon explosives or the previously used conventional fixed explosives, such'as gelatin dynamite, but they do have the advantage of lower cost. The primary difficulties experienced with this type of explosive are the relatively low strength of the explosive, the need for a large diameter in the charge and correspondingly large shot holes, relatively low rate of detonation, need to maintain maximum pressure on the charge, problem of packaging, the need for careful control of the carbon-ammonium nitrate ratio and the need for a detonation booster. The carbon-ammonium nitrate explosives have the further disadvantage common to the L.O.X. type of a relatively low and narrow range of density.

The present invention provides an explosive which has a much lower fire sensitivity and detonation sensitivity than the L.O.X. explosives and is much less expensive. The explosive of the present invention does not have the criticality of the ammonium nitrate-carbon mixture.

It does 'have much 'better performance characteristics 2,879,149 Patented Mar. 2.4, 19:59

, 2 than the L.O.X. explosives and the standard xed explosives such as sixty (60%) percent gelatin `dynamite type. The explosive of the present invention can be made with a variable density up to a relatively high density and higher gas releasing ability than either L.O.X. explosives or the carbon-ammonium nitrate explosives and at very low cost, so as to provide good shattering characteristics, along with the ability to do a large amount of work per unit volume.

I have discovered that ammonium nitrate admixed with certain carbonaceous materials in proper proportions and saturated with liquid oxygen will provide an explosive mixture far superior to anything heretofore proposed and at a cost below that of any of the heretofore proposed explosives. The explosive of my invention is less sensitive to detonation prior to the addition of liquid oxygen than -is ammonium nitrate alone. It is also less sensitive to lire and to premature explosion than the L.O.X. types of explosives and yet is sufficiently sensitive to be exploded without the need of boosters, such as are required in the ammonium nitrate carbon explosives which have been heretofore proposed.

I have found that an explosive made up of ammonium nitrate and carbon black such as the group lamp black or gas black in the proportions of not less than about ten (10%) percent by weight lamp or carbon black and saturated with liquid oxygen has explosive properties far superior to any explosive heretofore proposed per unit cost. The preferred composition of my explosive is about twenty (20%) percent by Weight of carbonaceous material and eighty percent by weight ammonium nitrate saturated with liquid oxygen. The proportion of carbonaceous material may be increased to eighty (80%) percent by weight or more but too large a proportion of carbonaceous material increases the shock or impact sensitivity as Well as the cost.

I have found that a portion of the carbon black may be replaced with graphite or low volatile coal of line particle sizes. There must, however, remain sufficient lamp black or gas black to coat the particles of graphitey or low volatile coal. If suicient lamp black is not re- -tained to accomplish this purpose, the explosive is-too sensitive to detonation. I have found that the amount of lamp black Will vary depending on the particle size in the mixture which determines the amount needed to coat the particles of graphite or low volatilev coal. This mixture, using graphite or low volatile coal coated' with carbon black favors the production of free-pouring qualities and may be made to pour into a Ibore hole without the need for forming the material into a cartridge.

The explosive of this invention may have a wide range of densities depending upon its composition and the use to which it is to be put. For example, the density may be increased by the use of graphite or low volatile coal Within the limits pointed out above. In addition, the density may be varied or controlled by controlling the physical size of the ammonium nitrate particles. Finely ground ammonium nitrate, for example, will produce higher densities than loose crystalline ammonium nitrate. By properly proportioniug the materials it is thus possible to get a high density, freely pouring material which can be poured directly into the bore hole and saturated with oxygen in situ.

I have also found that the density and resistance to fire can be substantially improved by the presence of water in the mixture without material impairment of the explosive characteristics. For example, a cartridge made up of about twenty (20%) percent by weight carbon, about twenty (20%) percent by Weight pelletized NH4NO3 and the balance a solution in water of NH4NO3 containing eighty-three (83%) percent by weight -NHNO3, will not ignite,leven when saturated with liquid `explclrsive of this invention which will be more readily 21,879,149 3 n 4 oxygen whereas a plain L.O.X. cartridge under lthe same Oxygen Explosives. U.S. Bureau of Mines Bulletin conditions will ignite and burn with an intense ame 472 (1949), particularly pages 61 to 64. similar to that of an Oxy-acetylene torch. A

I hav@ discovered `a new method of Thes methods give gOOd Values fOr E but SOmeWhat less precise values for D. They are, however, quite adequate for a comparison of performance values of explosives. The values of D and E given in Table I are computed but the computed -values check quite closely with actual measured values for sixty (60%) percent gelatin dynamite in liquid oxygen carbon explosives. In the table, it should be noted that the rate 'of a liquid oxygen explosive does not vary appreciably with the average oxygen condition over a wide range because the rate is determined by that `of the liquid oxygen saturated core of the cartridge.

`understood by reference to the accompanying drawing showing a vertical section through a bore hole. lorrn a `bore or shot hole in the material 11 to be blasted. This may be done by conventional drilling or jet piercing. A flexible plastic liner 12, such as a polyethylene bag, 10 ,is inserted into the hole 10, and a mixture 13 of about twenty percent by weightof `a low volatile coal `coated with lamp black and eighty (80%) percent by weight ammonium nitrate is poured into the bag. The mixture of ammonium nitrate and coal is preferably Table I.-Camparison of the explosive of this invention with other selected explosives Oxygen con- Absorb- Overall D E Ed Ratio of Ratio of ato of Explosive Composition, perdition, perent dendensity, meters] calories/ calories]` `D to Ed to B E'Dd cent by wt. cent of stoisity, g'mJcc. sec. gm. cc. 60% gel 60% gel to 60% chiometric gru/ce. gel

`1 60%.gelatin dynal. 45 6, 000 l, 000 1, 450 l. 0 1.0 1. 0

m1 e. 2 Lox {gggg gfgi-H fsspatea o. an 1. 24 5,100 1, ass 1.717 .85 1.18 1.01 3 Lex 2%; ff-m }11`o. o. ao 1.135A 5,100 i 1, 420 1, 612 .85 1.11 .945

46 5% NH4N O3. 4 Explosive of this 41.9% oxygen saturated, 0. 8,2 1. 411 6, 440 974 1, 374 1.07 95 1.02

invention. 11 6% lamp blaek 141.

58 2% NHiNOa 5 d0 27.2% oxygen saturated, 1.078 1. 495 i 7,400 -1, 172 1,752 1. `23 1. 2l `1..-19

14.6% lamp black, 100.

cooled to a temperature approximating that of liquid oxygen. An oxygen lance 14 is inserted through the mixture to the bottom of the bag and liquid oxygen is added until the mass of the mixture is saturated and a `layer 15 of liquid oxygen lies above the mixture 13. Preferably, a bleeder line 16 surrounds the oxygen lance 14 and is provided with openings 17 therein to carry `o any volatilized oxygen and prevent lifting of the charge by gas expansion. The bleeder line 16 and lance 14 are removed, the hole is stemmed and ready `to be shot. This method of blasting is particularly advantageous where jet piercing is necessary because of the ability of `the charge to conform to the irregularities ofthe 4shot hole. This method may be practiced using any freeowing composition according to this invention.

The performance of the explosive prepared according to my invention, is appreciably better than the standard liquid oxygen-carbon explosive, as Well as the xed explosives of the sixty (60%) percent gelatin dynamite type. It is generally accepted that for most blasting in heavy material, such as rock, it is desirable to make the energy release per unit volume and the rate of detonation as high as possible. The energy release per unit volumeis ,the `heat of explosion, E, times the overall density of the explosive cartridge, d. The rate of detonation, j), is the velocity of decomposition of an explosive column detonated at one end. The best single index of performance `seems to be the so-called brisance which is most often defined as B=EdD. In Table I, I have given comparative performance values calculated for the explosive of my invention and other competitive explosives. The computations for the table were made using the methods outlined in the following publications:

(l) F. W. Brown- Theoretcal Calculations gfor Explosives. I. Explosion Temperatures and Gaseous Products and Effects of Changes in Carbonaceous Materials. U.S. Bureau -of Mines Technical Paper 632 (A1941).

(2,) yF. `W. Brown-Theoretical Calculations for Explosives. II. Explosion Pressures. U.S/. Bureau Iof MinesTechnicalPaper 643 `(1942.)

.(6) Tournay, F-

;Bower and W- flitoral-- zafety and .Permanence Charactetisties ,ef .sulla An advantage of the explosive of my invention `is that the `density may be varied greatly. The density may be increased by increasing the fineness of the ammonium lnitrate or by the addition of graphite or low volatile v,coal as previously explained `Without in any way detrimentally affecting the performance of the explosive and without dctracting in any way from the advantages .which have been set out above.

The explosive of my invention may be detonated with any conventional detonator, such as those used with the xed explosives, and does not require the use of any special booster. It is an extremely low cost explosive but with a very high performance and fills the need for an explosive which may be safely and readily transported and handled ,prior to insertion in the bore hole and yet with sulicient sensitivity and detonatability to be tired without the conjoint use of expensive fixed ex-v `material selected from the group consisting of Vlamp blacl: and gas black, admixed `with suicientammonium `nitrate to make 100% by .weight andthe resulting `mixture saturated with liquid oxygen.

2. An explosive composition consisting `essentially of about 20% by weight of at least one material selected from the group consisting of lamp blackandgas .blackfad- `mixed with about by weight ammonium nitrate,

the resulting mixture being saturated with liquid oxygen. `3. An explosive composition consisting essentially of at` least onebase material selected from thegroup conqsistirig of graphite `and lovl volatile coal, `coated with a Vmaterial selected Vfromfthe group consisting of lamp blaclc and gas black, the `total amount `of base .merial and .coating .material being not less than @bevi 10% t0 ehem 180% vby weslitednixd withuifiieat amnesia.

nitrate to make 100% by weight and the resulting mixture saturated with liquid oxygen.

4. An explosive composition consisting essentially of at least one/base material selected from the group consisting of graphite and low volatile coal coated with a material selected from the group consisting of lamp black and gas black, the total amount of the base material and coated material being about 20% by weight admixed with suicient ammonium nitrate to make 100% by weight and the resulting mixture saturated with liquid oxygen.

5. An explosive composition consisting essentially of at least about to about 80% by weight of at least one material selected from the group consisting of lamp black and gas black, up to about 10% by weight water admixed with sulicient ammonium nitrate to make 100% by weight and the resulting mixture saturated with liquid oxygen.

6. An explosive composition consisting essentially of at least one base material selected from the group consisting of graphite and low volatile coal, coated with a material selected from the group consisting of lamp black and gas black, the total amount of base material and coating material being not less than about 10% to about 6 by weight, up to about 10% by weight water admixed with sufticient ammonium nitrate to make by weight and the resulting mixture saturated with liquid oxygen.

References Cited in the tile of this patent UNITED STATES PATENTS 371,298 Bourne Oct. 11, 1887 1,041,745 Corbin Oct. 22, 1912 1,131,994 Claude Mar. 16, 1915 1,440,041 Weber Dec. 26, 1922 1,860,816 Perrott et al. May 31, 1932 1,960,907 Holderer May 29, 1934 2,406,572 Vogl Aug. 27, 1946 2,704,515 lBarlowl Mar. 22, 1955 2,723,188 Barlow Nov. 8, 1955 2,745,346 Aitchison et al May l5, 1956 OTHER REFERENCES Rice: Development of Liquid Oxygen Explosives During the War, publ. by Govt Printing Office, Washington, D. C. (1920); Technical Paper 243, Bureau of Mines, pp. 7-9 and 23-25 relied on. 

1. AN EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF AT LEAST ABOUT 10% TO BAOUT 80% BY WEIGHT OF AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF LAMP BLACK AND GAS BLACK, ADMIXED WITH SUFFICIENT AMMONIUM NITRATE TO MAKE 100% BY WEIGHT AND THE RESULTING MIXTURE SATURATED WITH LIQUID OXYGEN. 